Impedance-to-digital converter, impedance-to-digital converting device, and method for adjustment of impedance-to-digital converting device

ABSTRACT

An impedance-to-digital converter is provided. A sensible impedance range of the impedance-to-digital converter is adjustable by changing magnitudes of signals inputted thereto.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/259,187, filed by the applicant on Sep. 8, 2016, the entiredisclosure of which is incorporated herein by reference, and whichclaims priority of Taiwanese Patent Application No. 104140663, filed onDec. 4, 2015.

FIELD

The disclosure relates to a conversion device, and more particularly toan impedance-to-digital converting device.

BACKGROUND

A conventional capacitance-to-digital technique is used for sensingcapacitance of a capacitor, and uses a limited number of digital codesto represent the different capacitances sensed thereby. Accordingly, itis unable to achieve a high sensing resolution and a wide sensiblecapacitance range at the same time. FIG. 1 shows a relationship betweenthe sensible capacitance ranges and the sensing resolutions of aconventional capacitance-to-digital converter that has multiple sensiblecapacitance ranges with different sensing resolutions. Assuming that theconventional capacitance-to-digital converter of FIG. 1 uses one hundreddigital codes to represent the capacitances sensed thereby, the sensingresolution is inversely proportional to capacitance variation per unitincrement of the digital code (i.e., a greater capacitance variation perchange of the digital code indicating a lower sensing resolution).Accordingly, in FIG. 1, a unit increment of the digital code representscapacitance variation of 0.14 pF in a sensible capacitance range of 2pF-16 pF, a unit increment of the digital code represents capacitancevariation of 0.48 pF in a sensible capacitance range of 16 pF-64 pF, anda unit increment of the digital code represents capacitance variation of1.92 pF in a sensible capacitance range of 64 pF-256 pF. Thus, such aconventional capacitance-to-digital converter is unable to achieve ahigh resolution when sensing a larger capacitor.

SUMMARY

Therefore, an object of the disclosure is to provide animpedance-to-digital converter that may alleviate the drawback of theprior art.

According to the disclosure, the impedance-to-digital converter isprovided for sensing an impedance value of a to-be-sensed component, andincludes a sensing unit, an offset impedance unit, a reference impedanceunit and a conversion block.

The sensing unit is to be coupled to the to-be-sensed component, isdisposed to receive a sensing voltage and a sensing current, is operableto select one of the sensing voltage and the sensing current to be asensing signal, and is configured to provide the sensing signal to theto-be-sensed component, and to convert the sensing signal into a firstelectric charge every operation period of the impedance-to-digitalconverter. An amount of the first electric charge of theimpedance-to-digital converter is proportional to a magnitude of thesensing signal. The offset impedance unit is disposed to receive anoffset signal, and is configured to convert the offset signal into asecond electric charge every operation period of theimpedance-to-digital converter. An amount of the second electric chargeis proportional to a magnitude of the offset signal. The referenceimpedance unit is disposed to receive a reference signal and a digitalsignal, and includes a reference impedance circuit configured to convertthe reference signal into a third electric charge every operation periodof the impedance-to-digital converter. An amount of the third electriccharge is proportional to a magnitude of the reference signal. Apolarity of the third electric charge is associated with a logic levelof the digital signal. The conversion block receives the first electriccharge, the second electric charge and the third electric charge thatare respectively outputted by the sensing unit, the offset impedanceunit and the reference impedance unit to cooperatively form a resultantelectric charge, and is configured to convert the resultant electriccharge into the digital signal. The impedance value sensed by theimpedance-to-digital converter has a linear relationship with a numberof the operation periods that correspond to a predetermined logic levelof the digital signal among a predetermined number of the operationperiods. A central value of a sensible impedance range is proportionalto a ratio of a magnitude of the offset signal to a magnitude of thesensing signal.

Another object of the disclosure is to provide an impedance-to-digitalconverting device that may alleviate the drawback of the prior art.

According to the disclosure, the impedance-to-digital converting deviceis provided for sensing an impedance value of a to-be-sensed component,and includes an impedance-to-digital converter of this disclosure, andan operation unit.

The operation unit is coupled to the conversion block for receivingtherefrom the digital signal, and is configured to perform an averageoperation of a series of logic values of the digital signal to generatea series-average value. The operation unit includes a lookup tablerecording a pre-stored impedance value that corresponds to theseries-average value thus generated, and is further configured to obtainthe pre-stored impedance value from the lookup table according to theseries-average value, and to output the pre-stored impedance value toserve as a sensed impedance value corresponding to the to-be-sensedcomponent. The impedance value sensed by the impedance-to-digitalconverting device has a linear relationship with a number of theoperation periods that correspond to a predetermined logic level of thedigital signal among a predetermined number of the operation periods. Acentral value of a sensible impedance range of the impedance-to-digitalconverter is proportional to a ratio of a magnitude of the offset signalto a magnitude of the sensing signal. The impedance value sensed byimpedance-to-digital converting device has a sensing resolutionproportional to a ratio of the magnitude of the sensing signal to amagnitude of the reference signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent inthe following detailed description of the embodiment (s) with referenceto the accompanying drawings, of which:

FIG. 1 is a plot illustrating a relationship among sensible capacitanceranges and the sensing resolutions of a conventionalcapacitance-to-digital converter;

FIG. 2 is a schematic circuit diagram illustrating an embodiment of theimpedance-to-digital converting device according to this disclosure;

FIG. 3 is a schematic circuit diagram illustrating a first variation ofthe embodiment;

FIG. 4 is a timing diagram of the first variation;

FIG. 5 is a plot illustrating a sensible impedance range of the firstvariation;

FIG. 6 is a plot illustrating a dynamic sensible impedance range of thefirst variation;

FIG. 7 is a plot illustrating a dynamic sensing resolution of the firstvariation;

FIGS. 8 and 9 are plots illustrating simulation results of the firstvariation;

FIG. 10 is a schematic circuit diagram illustrating a second variationof the embodiment;

FIG. 11 is a schematic circuit diagram illustrating a third variation ofthe embodiment;

FIG. 12 is a plot illustrating a sensible impedance range of the thirdvariation;

FIG. 13 shows a plot illustrating simulation results of the secondvariation;

FIG. 14 is a schematic circuit diagram illustrating a variation of asensing unit of the embodiment;

FIG. 15 is a schematic circuit diagram illustrating a fourth variationof the embodiment;

FIG. 16 is a plot illustrating a sensible impedance range of the fourthvariation;

FIG. 17 is a schematic circuit diagram illustrating a fifth variation ofthe embodiment;

FIG. 18 is a schematic circuit diagram illustrating operation of asensing unit of the fifth variation when a capacitor is a to-be-sensedcomponent; and

FIG. 19 is a schematic circuit diagram illustrating operation of asensing unit of the fifth variation when a resistor is a to-be-sensedcomponent.

DETAILED DESCRIPTION

Before the disclosure is described in greater detail, it should be notedthat where considered appropriate, reference numerals or terminalportions of reference numerals have been repeated among the figures toindicate corresponding or analogous elements, which may optionally havesimilar characteristics.

Referring to FIG. 2, the embodiment of the impedance-to-digitalconverting device 2 is provided for sensing an impedance value of ato-be-sensed component (ZS), and generates a sensed impedance valuecorresponding to the to-be-sensed component (ZS). Theimpedance-to-digital converting device 2 includes animpedance-to-digital converter 3 and an operation unit 9. In thisembodiment, the to-be-sensed component (ZS) has a first terminal and asecond terminal, and the impedance-to-digital converter 3 includes asensing unit 4, an offset impedance unit 5, a reference impedance unit600, a conversion block 7 and a signal generating unit 8.

The sensing unit 4 is coupled to the to-be-sensed component (ZS),receives a sensing signal, and periodically converts the sensing signalinto a first electric charge (Q1) by providing, within every operationperiod of the impedance-to-digital converter, the sensing signal to theto-be-sensed component (ZS). An amount of the first electric charge (Q1)is proportional to a magnitude of the sensing signal. In thisembodiment, the sensing unit 4 includes four sensing switches 41-44.

The sensing switch 41 receives a first control signal (φ1), introducesthe sensing signal to the first terminal of the to-be-sensed component(ZS) when conducting, and is configured to conduct or not conductaccording to the first control signal (φ1).

The sensing switch 42 receives the first control signal (φ1), couplesthe second terminal of the to-be-sensed component (ZS) to ground whenconducting, and is configured to conduct or not conduct according to thefirst control signal (φ1).

The sensing switch 43 receives a second control signal (φ2), introducesa reference signal to the first terminal of the to-be-sensed component(ZS) when conducting, and is configured to conduct or not conductaccording to the second control signal (φ2).

The sensing switch 44 receives the second control signal (φ2), has afirst terminal at which the first electric charge (Q1) is outputted whenthe sensing switch 44 is conducting, and a second terminal coupled tothe second terminal of the to-be-sensed component (ZS), and isconfigured to establish or not establish connection between the firstand second terminals thereof to be conducting or non-conductingaccording to the second control signal (φ2).

The offset impedance unit 5 receives an offset signal, and converts theoffset signal into a second electric charge (Q2) periodically (namely,every operation period of the impedance-to-digital converter). An amountof the second electric charge (Q2) is proportional to a magnitude of theoffset signal. In this embodiment, the offset impedance unit 5 includesan offset impedance component (ZSUB) and four offset switches 51-54.

The offset impedance component (ZSUB) has a first terminal and a secondterminal.

The offset switch 51 receives the first control signal (φ1), introducesthe offset signal to the first terminal of the offset impedancecomponent (ZSUB) when conducting, and is configured to conduct or notconduct according to the first control signal (φ1).

The offset switch 52 receives the first control signal (φ1), couples thesecond terminal of the offset impedance component (ZSUB) to ground whenconducting, and is configured to conduct or not conduct according to thefirst control signal (φ1).

The offset switch 53 receives the second control signal (φ2), has afirst terminal at which the second electric charge (Q2) is outputtedwhen the offset switch 53 is conducting, a second terminal coupled tothe first terminal of the offset impedance component (ZSUB), and isconfigured to establish or not establish connection between the firstand second terminals thereof to be conducting or non-conductingaccording to the second control signal (φ2).

The offset switch 54 receives the second control signal (φ2), introducesthe reference signal to the second terminal of the offset impedancecomponent (ZSUB) when conducting, and is configured to conduct or notconduct according to the second control signal (φ2).

The reference impedance unit 600 receives the reference signal and adigital signal (VD), and includes a reference impedance circuit 6 thatconverts the reference signal into a third electric charge (Q3)periodically (namely, every operation period of the impedance-to-digitalconverter) in this embodiment. An amount of the third electric charge(Q3) is proportional to a magnitude of the reference signal, and apolarity of the third electric charge (Q3) is associated with a logiclevel of the digital signal (VD). In detail, the reference impedanceunit 600 further includes two AND gates (A1, A2), and the referenceimpedance circuit 6 includes a reference impedance component (ZREF) andsix reference switches 61-66, but this disclosure is not limitedthereto.

The AND gate (A1) performs AND operation on the digital signal (VD) andthe first control signal (φ1) so as to generate a first operation signal(out1).

The AND gate (A2) perform AND operation on the first control signal (φ1)and an inverted digital signal that is complementary to the digitalsignal (VD) so as to generate a second operation signal (out2).

The reference impedance component (ZREF) has a first terminal and asecond terminal.

The reference switch 61 is coupled to the AND gate (A1) to receive thefirst operation signal (out1) therefrom, introduces the reference signalto the first terminal of the reference impedance component (ZREF) whenconducting, and is configured to conductor not conduct according to thefirst operation signal (out1).

The reference switch 62 is coupled to the AND gate (A1) to receive thefirst operation signal (out1) therefrom, couples the second terminal ofthe reference impedance component (ZREF) to ground when conducting, andis configured to conduct or not conduct according to the first operationsignal (out1).

The reference switch 63 receives the second control signal (φ2), has afirst terminal at which the third electric charge (Q3) is outputted whenthe reference switch 63 is conducting, and a second terminal coupled tothe first terminal of the reference impedance component (ZREF), and isconfigured to establish or not establish connection between the firstand second terminals thereof to be conducting or non-conductingaccording to the second control signal (φ2).

The reference switch 64 receives the second control signal (φ2),introduces the reference signal to the second terminal of the referenceimpedance component (ZREF) when conducting, and is configured to conductor not conduct according to the second control signal (φ2).

The reference switch 65 is coupled to the AND gate (A2) to receive thesecond operation signal (out2) therefrom, couples the first terminal ofthe reference impedance component (ZREF) to ground when conducting, andis configured to conduct or not conduct according to the secondoperation signal (out2).

The reference switch 66 is coupled to the AND gate (A2) to receive thesecond operation signal (out2) therefrom, introduces the referencesignal to the second terminal of the reference impedance component(ZREF) when conducting, and is configured to conduct or not conductaccording to the second operation signal (out2).

Accordingly, when both of the digital signal (VD) and the first controlsignal (φ1) have a high voltage level (i.e., logic “1”), the firstoperation signal (out1) has a high voltage level and the referenceswitches 61, 62 conduct, while the second operation signal (out2) has alow voltage level and the reference switches 65, 66 do not conduct. Whenthe digital signal (VD) has a low voltage level (i.e., logic 0) and thefirst control signal (φ1) has the high voltage level, the firstoperation signal (out1) has a low voltage level and the referenceswitches 61, 62 do not conduct, while the second operation signal (out2)has a high voltage level and the reference switches 65, 66 conduct.

The conversion block 7 receives the first electric charge (Q1), thesecond electric charge (Q2) and the third electric charge (Q3) that arerespectively outputted by the sensing unit 4, the offset impedance unit5 and the reference impedance unit 6 to cooperatively form a resultantelectric charge, and converts the resultant electric charge into thedigital signal (VD). In this embodiment, the conversion block 7 includesan integrator unit 70 and a voltage-to-digital unit 71.

The integrator unit 70 receives the first, second and third electriccharges (Q1, Q2, Q3) that cooperatively form the resultant electriccharge, and converts the resultant electric charge into an integratorvoltage (VINT). The integrator unit 70 of this embodiment includes anoperational amplifier (OP1) and an integrator capacitor (CINT).

The operational amplifier (OP1) has a first input (−, representing aninverting input) coupled to the first terminals of the sensing switch44, the offset switch 53 and the reference switch 63 for respectivelyreceiving therefrom the first, second and third electric charges (Q1,Q2, Q3) to cooperatively form the resultant electric charge, a secondinput (+, representing a non-inverting input) receiving the referencesignal, and an output at which the integrator voltage (VINT) isoutputted.

The integrator capacitor (CINT) is coupled between the first input (−)and the output of the operational amplifier (OP1).

The voltage-to-digital unit 71 is coupled to the integrator unit 70 forreceiving therefrom the integrator voltage (VINT), and converts amagnitude of the integrator voltage (VINT) into the digital signal (VD).The voltage-to-digital unit 71 of this embodiment includes a comparatorand a D flip-flop (DF).

In this embodiment, the comparator of the voltage-to-digital unit 71 isimplemented using an operational amplifier (OP2) that has a first input(−) coupled to the output of the integrator unit 70 for receivingtherefrom the integrator voltage (VINT), a second input (+) receivingthe reference signal, and an output at which a comparison signal (VCP)is outputted.

The D flip-flop (DF) has a data input (D) coupled to the output of theoperational amplifier (OP2), a clock input receiving a clock signal(CLK), an inverting output (Q) at which the digital signal (VD) isoutputted, and a non-inverting output (Q) at which the inversed digitalsignal is outputted.

The signal generating unit 8 is configured to generate the desiredsensing signal, offset signal, reference signal, first control signal(φ1), second control signals (φ2) and clock signal (CLK).

The operation unit 9 is coupled to the voltage-to-digital unit 71 forreceiving therefrom the digital signal (VD), and performs an averageoperation on a series of logic values of the digital signal (VD) togenerate a series-average value. In thi s embodiment, the operation unit9 includes a lookup table recording a plurality of pre-stored impedancevalues that correspond to different series-average values, so that theoperation unit 8 may obtain from the lookup table a pre-stored impedancevalue that corresponds to the series-average value thus generated, andthen output the obtained pre-stored impedance value in digital format toserve as a sensed impedance value corresponding to the to-be-sensedcomponent (ZS).

Referring to FIG. 3, a first variation of the embodiment is shown thatthe to-be-sensed component (ZS) includes a to-be-sensed capacitor (CS)having the first and second terminals of the to-be-sensed component(ZS), that the offset impedance component (ZSUB) includes an offsetcapacitor (CSUB), that the reference impedance component (ZREF) includesa reference capacitor (CREF), that the sensing signal includes a sensingvoltage (VSEN), that the offset signal includes an offset voltage(VOFF), and that the reference signal includes a reference voltage(VREF).

Operations of the embodiment are exemplified using the first variationhereinafter. It is noted that in this disclosure, each of the switchesconducts upon receipt of a high voltage level at a control terminalthereof, and does not conduct upon receipt of a low voltage level at thecontrol terminal thereof, but the disclosure is not limited thereto.Referring to FIG. 4, durations where the first control signal (φ1)causes the corresponding switches (e.g., the sensing switches 41, 42) toturn on (i.e., to conduct) do not overlap durations where the secondcontrol signal (φ2) causes the corresponding switches (e.g., the sensingswitches 43, 44) to turn on, so the sensing switches 41, 42 and thesensing switches 43, 44 do not conduct at the same time. Before thethird rising edge of the second control signal (φ2), the comparisonsignal (VCP) is logic “1”, causing the digital signal (VD) to be logic“0”, since the integrator voltage (VINT) is lower than the referencevoltage (VREF); during this time, the reference switches 61, 62 alwaysdo not conduct, and the reference switches 65, 66 conduct when the firstcontrol signal (φ1) is logic “1”. By cooperation of the operations ofthe reference switches 61-66 and the operational amplifier (OP2) thatreceives the reference voltage (VREF) at the second input (+) thereof,the integrator voltage (VINT) increases by ΔV1 at every rising edge ofthe second control signal (φ2) until the integrator voltage (VINT) isgreater than the reference voltage (VREF). In FIG. 4, since theintegrator voltage (VINT) becomes greater than the reference voltage(VREF) at the third rising edge of the second control signal (φ2), theintegrator voltage (VINT) has increased by ΔV1 for three times. It isnoted that a number of increments of ΔV1 is associated with apredetermined analog signal received at the second terminal (+) of theoperational amplifier (OP2), which is the reference voltage (VREF) inthis variation of the embodiment, but this disclosure is not limitedthereto. Once the integrator voltage (VINT) is greater than thereference voltage (VREF), the comparison signal (VCP) becomes logic “0”,and the digital signal (VD) becomes logic “1” at the next rising edge ofthe clock signal (CLK). Then, the reference switches 61, 62 conduct whenthe first control signal (φ1) is logic “1”, and the reference switches65, 66 do not conduct, followed by the integrator voltage (VINT)dropping by ΔV2 at the next rising edge of the second control terminal(φ2), where

${\Delta\; V\; 1} = {{V_{SEN} \times \frac{C_{SEN}}{C_{INT}}} - {V_{OFF} \times \frac{C_{SUB}}{C_{INT}}} + {V_{REF} \times \frac{C_{REF}}{C_{INT}}}}$${\Delta\; V\; 2} = {{V_{SEN} \times \frac{C_{SEN}}{C_{INT}}} - {V_{OFF} \times \frac{C_{SUB}}{C_{INT}}} - {V_{REF} \times \frac{C_{REF}}{C_{INT}}}}$with the parameters defined as follows:

-   V_(SEN): magnitude of sensing voltage-   V_(OFF): magnitude of offset voltage-   V_(REF): magnitude of reference voltage-   C_(INT): capacitance of integrator capacitor-   C_(SEN): capacitance of to-be-sensed capacitor-   C_(SUB): capacitance of offset capacitor-   C_(REF): capacitance of reference capacitor

According to capacitor charge balance, the following equation (1) may bederived based on charge transfer among the to-be-sensed capacitor (CS),the offset capacitor (CSUB), the reference capacitor (CREF) and theintegrator capacitor (CINT) within N operation periods (with one cycleof the clock signal (CLK) defining one operation period):N×C _(SEN) ×V _(SEN) −N×C _(SUB) ×V _(OFF) −Z×C _(REF) ×V _(REF)+(N−Z)×C_(REF) ×V _(REF)=0  (1)with the parameters defined below

-   N: number of operation periods-   Z: number of operation periods that correspond to a predetermined    logic level (e.g., logic “1”) of digital signal within N operation    periods

According to equation (1), the series-average value (Z/N) may be derivedas follows:

$\begin{matrix}{\frac{Z}{N} = \frac{{C_{SEN} \times V_{SEN}} - {C_{SUB} \times V_{OFF}} + {C_{REF} \times V_{REF}}}{2 \times C_{REF} \times V_{REF}}} & (2)\end{matrix}$

Referring to FIG. 5, a sensible impedance range of the first variationof the embodiment is illustrated by describing a relationship betweenthe series-average value and the corresponding capacitance obtainedaccording to equation (2) (i.e., the sensed impedance value). Inpractice, the lookup table of the operating unit 9 may be made accordingto such a relationship. The sensible impedance range may be described asfollows:

$\begin{matrix}{{{C_{SUB} \times \frac{V_{OFF}}{V_{SEN}}} - {C_{REF} \times \frac{V_{REF}}{V_{SEN}}}} \leq C_{SEN} \leq {{C_{SUB} \times \frac{V_{OFF}}{V_{SEN}}} + {C_{REF} \times \frac{V_{REF}}{V_{SEN}}}}} & (3)\end{matrix}$According to FIG. 5, it can be seen that a central value of the sensibleimpedance (capacitance) range is

${C_{SUB} \times \frac{V_{OFF}}{V_{SEN}}},$that the sensed impedance (capacitance) value has a sensing resolutionproportional to

$\frac{V_{SEN}}{V_{REF}},$and that the sensed impedance value has a linear relationship with theseries-average value (Z/N). Since the number (N) of the operationperiods is predetermined, the sensed impedance value has a linearrelationship with the number (Z) of the operation periods thatcorrespond to the predetermined logic level of the digital signal withinthe predetermined number (N) of the operation periods.

According to the abovementioned equations, a method for adjustment ofthe impedance-to-digital converting device 2 according to thisdisclosure is provided as follows:

1. The central value of the sensible impedance range can be adjusted byusing the signal generating unit 8 to change the ratio of the magnitudeof the offset signal to the magnitude of the sensing signal (e.g.,V_(OFF)/V_(SEN)). FIG. 6 illustrates that the central value of thesensible impedance range is dynamically adjustable with a constantsensing resolution of the sensed impedance value.

2. The sensing resolution of the sensed impedance value can be adjustedby using the signal generating unit 8 to change the ratio of themagnitude of the sensing signal to the magnitude of the reference signal(e.g., V_(SEN)/V_(REF)). FIG. 7 illustrates that both of the sensingresolution of the sensed impedance value and the central value of thesensible impedance range are dynamically adjustable.

FIGS. 8 and 9 show simulation results of the sensible impedance range ofthe first variation of the embodiment with different combinations of thesensing signal (V_(SEN)), the offset signal (V_(OFF)) and the referencesignal (V_(REF)).

Referring to FIG. 10, a second variation of the embodiment is shown tobe similar to the first variation, and differs from the first variationin that, the second variation includes a plurality of the offsetimpedance units 5 ₁-5 _(n), a plurality of the reference impedancecircuits 6 ₁-6 _(n), an offset selector 50 and a reference selector 60.

In this variation, each of the offset impedance units 5 ₁-5 _(n) has aconfiguration the same as that of the offset impedance unit 5 of thefirst variation, and each of the reference impedance units 6 ₁-6 _(n)has a configuration the same as that of the reference impedance unit 6of the first variation.

The offset selector 50 has a plurality of inputs respectively coupled tothe first terminals of the offset switches 53 of the offset impedanceunits 5 ₁-5 _(n) for receiving the second electric charges (Q2)therefrom, and an output coupled to the integrator unit 70. The offsetselector 50 selectively provides at least one of the second electriccharges (Q2) to the integrator unit 70.

The reference selector 60 has a plurality of inputs respectively coupledto the first terminals of the reference switches 63 of the referenceimpedance circuits 6 ₁-6 _(n) for receiving the third electric charges(Q3) therefrom, and an output coupled to the integrator unit 70. Thereference selector 60 selectively provides at least one of the thirdelectric charges (Q3) to the integrator unit 70.

By virtue of the abovementioned configuration, equivalent capacitance ofthe offset capacitors (CSUB) may be changed by using the offset selector50 to select a desired number of the offset impedance units 5 ₁-5 _(n)to provide the second electric charges (Q2) to the integrator unit 70,and equivalent capacitance of the reference capacitors (CREF) may bechanged by using the reference selector 60 to select a desired number ofthe reference impedance circuits 6 ₁-6 _(n) to provide the thirdelectric charges (Q3) to the integrator unit 70. According torelationship (3), it is known that, in this variation, the central valueof the sensible impedance range may be adjusted by changing theequivalent capacitance of the offset capacitors (CSUB), and the sensingresolution of the sensed impedance value may be adjusted by changing theequivalent capacitance of the reference capacitors (CREF). In thisvariation, the user may use the signal generating unit 8 to generate anoffset select signal (VSEL1) to control selection of the offset selector50, and a reference select signal (VSEL2) to control selection of thereference selector 60.

Thus, for this variation, the method for adjustment of theimpedance-to-digital converting device 2 according to this disclosure isfurther provided as follows:

3. The central value of the sensible impedance range can be adjusted byusing the signal generating unit 8 to change the offset select signal(VSEL1) for adjusting a number of the second electric charges (Q2) to beprovided to the integrator unit 70 (i.e., adjusting the equivalentcapacitance of the offset capacitors (CSUB)).

4. The sensed impedance value can be adjusted by using the signalgenerating unit 8 to change the reference select signal (VSEL2) foradjusting a number of the third electric charges (Q3) to be provided tothe integrator unit 70 (i.e., adjusting the equivalent capacitance ofthe reference capacitors (CREF)).

Referring to FIG. 11, a third variation of the embodiment is shown to besimilar to the first variation, and differs from the first variation inthat the to-be-sensed component (ZS) is characterized as a resistor andincludes a to-be-sensed resistor (RS) having the first and secondterminals of the to-be-sensed component (ZS), and in the thirdvariation, the sensing signal includes a sensing current (ISEN), and thesensing unit 4 further includes a sensing capacitor (CSEN) coupled tothe to-be-sensed resistor (RS) in parallel. It is noted that the sensingcapacitor (CSEN) may be either an internal capacitor of theimpedance-to-digital converting device 2, or an external capacitor withrespect to the impedance-to-digital converting device 2.

Referring to FIG. 12, according to capacitor charge balance, a sensibleimpedance range of the third variation is shown to be:

$\begin{matrix}{{{\frac{C_{SUB}}{C_{SEN}} \times \frac{V_{OFF}}{I_{SEN}}} - {\frac{C_{REF}}{C_{SEN}} \times \frac{V_{REF}}{I_{SEN}}}} \leq R_{SEN} \leq {{\frac{C_{SUB}}{C_{SEN}} \times \frac{V_{OFF}}{I_{SEN}}} + {\frac{C_{REF}}{C_{SEN}} \times \frac{V_{REF}}{I_{SEN}}}}} & (4)\end{matrix}$with the parameters defined as follows:

-   R_(SEN): resistance of to-be-sensed resistor-   I_(SEN): magnitude of sensing current-   V_(OFF): magnitude of offset voltage-   V_(REF) magnitude of reference voltage-   C_(SEN): capacitance of sensing capacitor-   C_(SUB): capacitance of offset capacitor-   C_(REF): capacitance of reference capacitor

It is known from the above relationship that a central value of thesensible impedance range of the third variation is

${\frac{C_{SUB}}{C_{SEN}} \times \frac{V_{OFF}}{I_{SEN}}},$and a sensing resolution of the sensed impedance value is proportionalto

$\frac{I_{SEN}}{V_{REF}}.$

Furthermore, since the sensing current (I_(SEN)) may be represented interms of a relationship between a sensing voltage (V_(SEN)) and aninternal resistance (R_(B)) of the signal generating unit 8, i.e.,

${I_{SEN} = \frac{V_{SEN}}{R_{B}}},$relationship (4) can also be represented as:

$\begin{matrix}{{{\frac{C_{SUB}}{C_{SEN}} \times \frac{V_{OFF}}{V_{SEN}} \times R_{B}} - {\frac{C_{REF}}{C_{SEN}} \times \frac{V_{REF}}{V_{SEN}} \times R_{B}}} \leq R_{SEN} \leq {{\frac{C_{SUB}}{C_{SEN}} \times \frac{V_{OFF}}{V_{SEN}} \times R_{B}} + {\frac{C_{REF}}{C_{SEN}} \times \frac{V_{REF}}{V_{SEN}} \times R_{B}}}} & (5)\end{matrix}$

In other words, the sensible impedance range (or the sensing resolutionof the sensed impedance value) may be adjusted by changing V_(SEN), andis not limited by R_(B).

In practice, the user may first use appropriate parameter settings ofR_(B), C_(SUB), C_(SEN), C_(REF), V_(SEN), V_(OFF) and V_(REF) toperform sensing with a wider sensible impedance range to obtain a roughimpedance value of the to-be-sensed component (ZS). Then, the user mayshift the central value of the sensible impedance range according to therough impedance value, and narrow down the sensible impedance range toachieve a higher resolution of the sensed impedance value by changingthe abovementioned parameter setting. Accordingly, this disclosure mayachieve an effective wider sensible impedance range while maintaining ahigh sensing resolution of the sensing result with limited chip area.FIG. 13 shows simulation results of the sensible impedance range(R_(SENSOR)) of the third variation with different V_(SEN) and C_(SUB).

Referring to FIG. 14, a variation of the sensing unit 4 of theembodiment is shown to be similar to that shown in FIG. 2, and differstherefrom in that this variation is adapted to sense a to-be-sensedcomponent (ZS) having composite impedance (e.g., resistance andcapacitance). In this variation, the to-be-sensed component (ZS)includes a resistor (RS) and a capacitor (CS) that are coupled inparallel between the first and second terminals thereof, and the sensingunit 4 further includes a sensing switch 45, a sensing capacitor (CSEN)and a sensing switch 46 that are coupled in series in the given orderbetween the first and second terminals of the to-be-sensed component(ZS). When the resistance part (i.e., the resistor (RS)) is to besensed, the sensing capacitor (CSEN) is required, and thus the sensingswitches 45, 46 are switched to be conducting. On the other hand, thesensing capacitor (CSEN) is not required when the capacitance part(i.e., the capacitor (CS)) is to be sensed, and thus the sensingswitches 45, 46 are switched to be not conducting. Accordingly, thecomposite impedance of the to-be-sensed component (ZS) can be completed.

Referring to FIG. 17, another variation of the sensing unit 4 of theembodiment for sensing a to-be-sensed component (ZS) having compositeimpedance is shown that the sensing signal includes a sensing voltage(VSEN) and a sensing current (ISSN), the to-be-sensed component (ZS)includes a resistor (RS) and a capacitor (CS) that are coupled inparallel between the first and second terminals of the sensing unit 4,and the sensing unit 4 includes a multiplexer 40, four sensing switches41-44, a sensing capacitor (CSEN) and a switch unit 47.

The multiplexer 40 has a first input receiving the sensing voltage(VSEN), a second input receiving the sensing current (ISEN), and anoutput, and is operable to couple one of the first and second inputsthereof to the output thereof, thereby selectively providing the sensingvoltage (VSEN) or the sensing current (ISEN) at the output thereof.

The sensing switch 41 has a first terminal coupled to the output of themultiplexer 40, and a second terminal, and is configured to establish ornot establish connection between the first and second terminals thereofaccording to the first control signal (φ1).

The sensing switch 42 has a grounded first terminal, and a secondterminal, and is configured to establish or not establish connectionbetween the first and second terminals thereof according to the firstcontrol signal (φ1).

The sensing switch 43 has a first terminal receiving the referencevoltage (VREF), and a second terminal coupled to the second terminal ofthe sensing switch 41, and is configured to establish or not establishconnect ion between the first and second terminals thereof according tothe second control signal (φ2).

The sensing switch 44 has a first terminal at which the first electriccharge (Q1) is outputted when the sensing switch 44 is conducting, and asecond terminal coupled to the second terminal of the sensing switch 42,and is configured to establish or not establish connection between thefirst and second terminals thereof according to the second controlsignal (φ2). The switch unit 47 includes six switches (S1-S6). Theswitch (S1) is coupled between the second input of the multiplexer 40and the first terminal of the to-be-sensed component (ZS). The switch(S2) is coupled between the second terminal of the to-be-sensedcomponent (ZS) and ground. The switch (S3) is coupled between the secondterminal of the sensing switch 41 and the first terminal of theto-be-sensed component (ZS). The switch (S4) is coupled between thesecond terminal of the to-be-sensed component (ZS) and the secondterminal of the sensing switch 42. The switch (S5) is coupled betweenthe second terminal of the sensing switch 41 and a first terminal of thesensing capacitor (CSEN). The switch (S6) is coupled between a secondterminal of the sensing capacitor (CSEN) and the second terminal of thesensing switch 42.

As shown in FIG. 18, in a case that a capacitance part (i.e., thecapacitor (CS)) is to be sensed, the sensing capacitor (CSEN) is notrequired so the sensing switches (S5, S6) are switched to be notconducting. The multiplexer 40 is operated to couple the first input andthe output thereof together, the switches (S3, S4) are switched to beconducting, and the switches (S1, S2) are switched to be not conductingso that the sensing voltage (VSEN) is introduced to the first terminalof the capacitor (CS) for charging the capacitor (CS) when the firstcontrol signal (φ1) causes the sensing switches (41, 42) to beconducting. In this situation, the sensible impedance range may beexpressed as equation (3).

As shown in FIG. 19, in a case that a resistance part (i.e., theresistor (RS)) is to be sensed, the sensing capacitor (CSEN) is requiredso the sensing switches (S5, S6) are switched to be conducting. Themultiplexer 40 is operated to couple the second input and the outputthereof together, the switches (S3, S4) are switched to be notconducting, and the switches (S1, S2) are switched to be conducting sothat a voltage at the output and the second input of the multiplexer 40is introduced to the first terminal of the capacitor (CSEN) for chargingthe capacitor (CSEN) when the first control signal (φ1) causes thesensing switches (41, 42) to be conducting. The voltage at the outputand the second input of the multiplexer 40 results from the sensingcurrent (ISEN) and the resistor (RS), and has a magnitude ofI_(SEN)×R_(SEN), where I_(SEN) represents a magnitude of the sensingcurrent (ISEN), which may be represented in terms of a relationshipbetween a sensing voltage (V_(SEN)) and an internal resistance (R_(B))of the signal generating unit 8, i.e.,

${I_{SEN} = \frac{V_{SEN}}{R_{B}}},$and R_(SEN) represents resistance of the resistor (RS). In thissituation, the sensible impedance range may be expressed as equation (4)or (5).

Referring to FIG. 15, a fourth variation of the embodiment is shown tobe similar to the third variation, and differs from the third variationin that the offset signal includes an offset current (IOFF), and theoffset impedance component (ZSUB) of the offset impedance unit 5 furtherincludes an offset resistor (ROFF) coupled to the offset capacitor(CSUB) in parallel.

When the sensing unit 4 receives the sensing current (ISEN), the sensingcurrent (ISEN) flows through the to-be-sensed resistor (RS) to form avoltage (V_(SEN)=I_(SEN)×R_(SEN)), where I_(SEN) represents a magnitudeof the sensing current (ISEN), and R_(SEN) represents resistance of theto-be-sensed resistor (RS)) that is stored in the sensing capacitor(CSEN) and that is functionally equivalent to the sensing voltage (VSEN)of the first variation.

When the offset impedance unit 5 receives the offset current (IOFF), theoffset current (IOFF) flows through the offset resistor (ROFF) to form avoltage (V_(OFF)=I_(OFF)×R_(OFF)), where I_(OFF) represents a magnitudeof the offset current (IOFF), and R_(OFF) represents resistance of theoffset resistor (ROFF)) that is stored in the offset capacitor (CSUB)and that is functionally equivalent to the offset voltage (VOFF) of thethird variation.

In a similar manner, the reference voltage (VREF) may be generated by areference current (IREF) flowing through a reference resistor (RREF).

Referring to FIG. 16, according to capacitor charge balance, a sensibleimpedance range of the fourth variation is shown to be:

${{\frac{C_{SUB}}{C_{SEN}} \times \frac{I_{OFF}}{I_{SEN}} \times R_{OFF}} - {\Delta\; R_{SEN}}} \leq R_{SEN} \leq {{\frac{C_{SUB}}{C_{SEN}} \times \frac{I_{OFF}}{I_{SEN}} \times R_{OFF}} + {\Delta\; R_{SEN}}}$$\mspace{79mu}{{\Delta\; R_{SEN}} = {\frac{C_{REF}}{C_{SEN}} \times \frac{I_{REF}}{I_{SEN}} \times R_{REF}}}$with the parameters defined as follows:

-   R_(SEN): resistance of to-be-sensed resistor-   R_(OFF): resistance of offset resistor-   R_(REF) resistance of reference resistor-   I_(SEN): magnitude of sensing current-   I_(OFF): magnitude of offset current-   I_(REF): magnitude of reference current-   C_(SEN): capacitance of sensing capacitor-   C_(SUB): capacitance of offset capacitor-   C_(REF): capacitance of reference capacitor

In summary, the disclosure may have the following advantages:

1. The central value of the sensible impedance (including resistance andcapacitance) range and the sensing resolution of the sensed impedancevalue are both adjustable, thereby achieving an effective wider sensibleimpedance range while maintaining a high sensing resolution of thesensed impedance value.

2. The sensible impedance range may be shifted as desired by changingthe ratio of the magnitude of the offset signal to the magnitude of thesensing signal, where each of the offset signal and the sensing signalmay be either a voltage signal or a current signal.

3. The sensing resolution of the sensed impedance value may be adjustedby changing the ratio of the magnitude of the sensing signal to themagnitude of the reference signal, where each of the reference signaland the sensing signal may be either a voltage signal or a currentsignal.

4. The sensible impedance range is not limited by internal resistance ofthe chip.

5. Impedance-to-digital conversion implemented by the disclosedarchitecture may cover both of capacitance-to-digital conversion andresistance-to-digital conversion.

6. Applicable products of the disclosed impedance-to-digital convertingdevice may be significantly promoted. Capacitance sensing has a varietyof applications, such as accelerometers, pressure meters, humiditymeters, wearable devices, etc., with different requirements for thesensible impedance range and the sensing resolution. The sensibleimpedance range and the sensing resolution of the disclosedimpedance-to-digital converting device are both adjustable by changingmagnitudes of signal, thereby being suited to a variety of applications.

7. This disclosure may be applied to a wearable device market. Healthand fitness are the primarily desired functions for wearable devices, sohealth-related sensing devices, such as pulsemeter, pulse oximeter, skinmoisture sensors, etc., are important to the wearable device market.Environmental sensors, such as sensors for temperature, humidity,ultraviolet, gas (e.g., carbon monoxide), have high market potential.While doing exercise, microphones (voice sensors) may be used totransmit user's instructions, and motion sensors may be used to achieveposture control. Accelerometers, gyroscopes, MEMS microphones and pulsesensors may be implemented into smartwatches. More and more wearabledevices implement the abovementioned applications, thereby leading tohigh potential of the disclosure in the wearable device market.

8. Since the sensible impedance range and the sensing resolution of thedisclosure may be adjusted for different applications, high integritymay be achieved, thereby reducing cost of products.

In the description above, for the purposes of explanation, numerousspecific details have been set forth in order to provide a thoroughunderstanding of the embodiment (s). It will be apparent, however, toone skilled in the art, that one or more other embodiments may bepracticed without some of these specific details. It should also beappreciated that reference throughout this specification to “oneembodiment,” “an embodiment,” an embodiment with an indication of anordinal number and so forth means that a particular feature, structure,or characteristic may be included in the practice of the disclosure. Itshould be further appreciated that in the description, various featuresare sometimes grouped together in a single embodiment, figure, ordescription thereof for the purpose of streamlining the disclosure andaiding in the understanding of various inventive aspects.

While the disclosure has been described in connection with what is (are)considered the exemplary embodiment(s), it is understood that thisdisclosure is not limited to the disclosed embodiment(s) but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. An impedance-to-digital converter for sensing animpedance value of a to-be-sensed component, said impedance-to-digitalconverter comprising: a sensing unit to be coupled to the to-be-sensedcomponent, disposed to receive a sensing voltage and a sensing current,operable to select one of the sensing voltage and the sensing current tobe a sensing signal, and configured to provide the sensing signal to theto-be-sensed component, and to convert the sensing signal into a firstelectric charge every operation period of said impedance-to-digitalconverter, an amount of the first electric charge being proportional toa magnitude of the sensing signal; an offset impedance unit disposed toreceive an offset signal, and configured to convert the offset signalinto a second electric charge every operation period of saidimpedance-to-digital converter, an amount of the second electric chargebeing proportional to a magnitude of the offset signal; a referenceimpedance unit disposed to receive a reference signal and a digitalsignal, and including a reference impedance circuit configured toconvert the reference signal into a third electric charge everyoperation period of said impedance-to-digital converter, an amount ofthe third electric charge being proportional to a magnitude of thereference signal, a polarity of the third electric charge beingassociated with a logic level of the digital signal; and a conversionblock receiving the first electric charge, the second electric chargeand the third electric charge that are respectively outputted by saidsensing unit, said offset impedance unit and said reference impedanceunit to cooperatively form a resultant electric charge, and configuredto convert the resultant electric charge into the digital signal;wherein the impedance value sensed by said impedance-to-digitalconverter has a linear relationship with a number of the operationperiods that correspond to a predetermined logic level of the digitalsignal among a predetermined number of the operation periods; wherein acentral value of a sensible impedance range of said impedance-to-digitalconverter is proportional to a ratio of a magnitude of the offset signalto a magnitude of the sensing signal.
 2. The impedance-to-digitalconverter of claim 1, wherein the impedance value sensed by saidimpedance-to-digital converter has a sensing resolution proportional toa ratio of the magnitude of the sensing signal to a magnitude of thereference signal.
 3. The impedance-to-digital converter of claim 2, theto-be-sensed component having a first terminal and a second terminal,wherein said sensing unit includes: a multiplexer having a firstmultiplexer input to receive the sensing voltage, a second multiplexerinput to receive the sensing current, and a multiplexer output; a firstsensing switch disposed to receive a first control signal, having afirst terminal coupled to said multiplexer output, and a secondterminal, and configured to conduct or not conduct according to thefirst control signal; a second sensing switch disposed to receive thefirst control signal, having a grounded first terminal and a secondterminal, and configured to conduct or not conduct according to thefirst control signal; a third sensing switch disposed to receive asecond control signal, having a first terminal disposed to receive thereference signal, and a second terminal coupled to said second terminalof said first sensing switch, and configured to conduct or not conductaccording to the second control signal; a fourth sensing switch disposedto receive the second control signal, having a first terminal at whichthe first electric charge is outputted when said fourth sensing switchis conducting, and a second terminal coupled to said second terminal ofsaid second sensing switch, and configured to conduct or not conductaccording to the second control signal; a sensing capacitor having afirst terminal and a second terminal; and a switch unit coupled to saidsecond multiplexer input, said second terminal of said first sensingswitch, said first and second terminals of said sensing capacitor, andsaid second terminal of said second sensing switch, to be coupled to thefirst and second terminals of the to-be-sensed component, and operableto individually make or break electrical connections between said secondmultiplexer input and the first terminal of the to-be-sensed component,between said second terminal of said first sensing switch and the firstterminal of the to-be-sensed component, between the second terminal ofthe to-be-sensed component and said second terminal of said secondsensing switch, between said second terminal of said first sensingswitch and said first terminal of said sensing capacitor, and betweensaid second terminals of said sensing capacitor and said second sensingswitch; wherein said first sensing switch and said third sensing switchdo not conduct at the same time.
 4. The impedance-to-digital converterof claim 3, wherein said switch unit includes: a first switch to couplesaid second multiplexer input to the first terminal of the to-be-sensedcomponent when conducting; a second switch to couple the second terminalof the to-be-sensed component to ground when conducting; a third switchto couple said second terminal of said first sensing switch to the firstterminal of the to-be-sensed component when conducting; a fourth switchto couple said second terminal of said second sensing switch to thesecond terminal of the to-be-sensed component when conducting; a fifthswitch coupled between said second terminal of said first sensing switchand said first terminal of said sensing capacitor; and a sixth switchcoupled between said second terminals of said sensing capacitor and saidsecond sensing switch.
 5. The impedance-to-digital converter of claim 3,wherein said offset impedance unit includes: an offset capacitor havinga first terminal and a second terminal; a first offset switch disposedto receive the first control signal, to introduce the offset signal tosaid first terminal of said offset capacitor when conducting, andconfigured to conduct or not conduct according to the first controlsignal; a second offset switch disposed to receive the first controlsignal, to couple said second terminal of said offset capacitor toground when conducting, and configured to conduct or not conductaccording to the first control signal; a third offset switch disposed toreceive the second control signal, having a first terminal at which thesecond electric charge is outputted when said third offset switch isconducting, a second terminal coupled to said first terminal of saidoffset capacitor, and configured to establish or not establishconnection between said first and second terminals thereof to beconducting or non-conducting according to the second control signal; anda fourth offset switch disposed to receive the second control signal, tointroduce the reference signal to said second terminal of said offsetcapacitor when conducting, and configured to conduct or not conductaccording to the second control signal.
 6. The impedance-to-digitalconverter of claim 3, wherein said voltage-to-digital unit is furtherconfigured to generate an inverted digital signal that is complementaryto the digital signal, and said reference impedance unit furtherincludes: a first AND gate configured to perform AND operation on thedigital signal and the first control signal so as to generate a firstoperation signal; and a second AND gate configured to perform ANDoperation on the inverted digital signal and the first control signal soas to generate a second operation signal; wherein said referenceimpedance circuit includes: a reference capacitor having a firstterminal and a second terminal; a first reference switch coupled to saidfirst AND gate to receive the first operation signal therefrom, disposedto introduce the reference signal to said first terminal of saidreference capacitor when conducting, and configured to conduct or notconduct according to the first operation signal; a second referenceswitch coupled to said first AND gate to receive the first operationsignal therefrom, disposed to couple said second terminal of saidreference capacitor to ground when conducting, and configured to conductor not conduct according to the first operation signal; a thirdreference switch disposed to receive the second control signal, having afirst terminal at which the third electric charge is outputted when saidthird reference switch is conducting, and a second terminal coupled tosaid first terminal of said reference capacitor, and configured toestablish or not establish connection between said first and secondterminals thereof to be conducting or non-conducting according to thesecond control signal; a fourth reference switch disposed to receive thesecond control signal, to introduce the reference signal to said secondterminal of said reference capacitor when conducting, and configured toconduct or not conduct according to the second control signal; a fifthreference switch coupled to said second AND gate to receive the secondoperation signal therefrom, disposed to couple said first terminal ofsaid reference capacitor to ground when conducting, and configured toconduct or not conduct according to the second operation signal; and asixth reference switch coupled to said second AND gate to receive thesecond operation signal therefrom, disposed to introduce the referencesignal to said second terminal of said reference capacitor whenconducting, and configured to conduct or not conduct according to thesecond operation signal.
 7. The impedance-to-digital converter of claim3, comprising a plurality of said offset impedance units, and furthercomprising an offset selector having a plurality of inputs respectivelycoupled to said offset impedance units for receiving the second electriccharges therefrom, and an output coupled to said conversion block,wherein said offset selector is configured to selectively provide atleast one of the second electric charges to said conversion block. 8.The impedance-to-digital converter of claim 3, wherein said referenceimpedance unit includes a plurality of said reference impedancecircuits, said impedance-to-digital converter further comprising areference selector having a plurality of inputs respectively coupled tosaid reference impedance circuits for receiving the third electriccharges therefrom, and an output coupled to said conversion block,wherein said reference selector is configured to selectively provide atleast one of the third electric charges to said conversion block.
 9. Theimpedance-to-digital converter of claim 8, wherein saidvoltage-to-digital unit is further configured to generate an inverteddigital signal that is complementary to the digital signal; wherein saidreference impedance unit further includes: a first AND gate configuredto perform AND operation on the digital signal and the first controlsignal so as to generate a first operation signal; and a second AND gateconfigured to perform AND operation on the inverted digital signal andthe first control signal so as to generate a second operation signal;wherein each of said reference impedance circuits includes: a referencecapacitor having a first terminal and a second terminal; a firstreference switch coupled to said first AND gate to receive the firstoperation signal therefrom, disposed to introduce the reference signalto said first terminal of said reference capacitor when conducting, andconfigured to conduct or not conduct according to the first operationsignal; a second reference switch coupled to said first AND gate toreceive the first operation signal therefrom, disposed to couple saidsecond terminal of said reference capacitor to ground when conducting,and configured to conduct or not conduct according to the firstoperation signal; a third reference switch disposed to receive thesecond control signal, having a first terminal at which the thirdelectric charge is outputted when said third reference switch isconducting, and a second terminal coupled to said first terminal of saidreference capacitor, and configured to establish or not establishconnection between said first and second terminals thereof to beconducting or non-conducting according to the second control signal; afourth reference switch disposed to receive the second control signal,to introduce the reference signal to said second terminal of saidreference capacitor when conducting, and configured to conduct or notconduct according to the second control signal; a fifth reference switchcoupled to said second AND gate to receive the second operation signaltherefrom, disposed to couple said first terminal of said referencecapacitor to ground when conducting, and configured to conduct or notconduct according to the second operation signal; and a sixth referenceswitch coupled to said second AND gate to receive the second operationsignal therefrom, disposed to introduce the reference signal to saidsecond terminal of said reference capacitor when conducting, andconfigured to conduct or not conduct according to the second operationsignal.
 10. The impedance-to-digital converter of claim 3, the offsetsignal including an offset voltage, the reference signal including areference voltage, and the to-be-sensed component including ato-be-sensed capacitor that has the first and second terminals of theto-be-sensed component, wherein said offset impedance unit includes anoffset capacitor, said reference impedance unit includes a referencecapacitor, and said impedance-to-digital converter is configured tosatisfy:$\mspace{79mu}{{\frac{Z}{N} = \frac{{C_{SEN} \times V_{SEN}} - {C_{SUB} \times V_{OFF}} + {C_{REF} \times V_{REF}}}{2 \times C_{REF} \times V_{REF}}};{and}}$${{{C_{SUB} \times \frac{V_{OFF}}{V_{SEN}}} - {C_{REF} \times \frac{V_{REF}}{V_{SEN}}}} \leq C_{SEN} \leq {{C_{SUB} \times \frac{V_{OFF}}{V_{SEN}}} + {C_{REF} \times \frac{V_{REF}}{V_{SEN}}}}};$where “N” represents the predetermined number of the operation periods,“Z” represents the number of the operation periods that correspond tothe predetermined logic level of the digital signal among thepredetermined number of the operation periods, “C_(SEN)” represents theimpedance value of the to-be-sensed capacitor sensed by saidimpedance-to-digital converter, “C_(SUB)” represents capacitance of saidoffset capacitor, “C_(REF)” represents capacitance of said referencecapacitor, “V_(SEN)” represents a magnitude of the sensing voltage,“V_(OFF)” represents a magnitude of the offset voltage, and “V_(REF)”represents a magnitude of the reference voltage; wherein the centralvalue of the sensible impedance range of said impedance-to-digitalconverter is ${C_{SUB} \times \frac{V_{OFF}}{V_{SEN}}},$ and the sensingresolution of the impedance value sensed by said impedance-to-digitalconverter is proportional to $\frac{V_{SEN}}{V_{REF}}.$
 11. Theimpedance-to-digital converter of claim 3, the offset signal includingan offset voltage, the reference signal including a reference voltage,and the to-be-sensed component including a to-be-sensed resistor thathas the first and second terminals of the to-be-sensed component,wherein said offset impedance unit includes an offset capacitor, saidreference impedance unit includes a reference capacitor, and saidimpedance-to-digital converter is configured to satisfy:${{{\frac{C_{SUB}}{C_{SEN}} \times \frac{V_{OFF}}{I_{SEN}}} - {\frac{C_{REF}}{C_{SEN}} \times \frac{V_{REF}}{I_{SEN}}}} \leq R_{SEN} \leq {{\frac{C_{SUB}}{C_{SEN}} \times \frac{V_{OFF}}{I_{SEN}}} + {\frac{C_{REF}}{C_{SEN}} \times \frac{V_{REF}}{I_{SEN}}}}};$where “R_(SEN)” represents the impedance value of the to-be-sensedresistor sensed by said impedance-to-digital converter, “C_(SEN)”represents capacitance of said sensing capacitor, “C_(SUB)” representscapacitance of said offset capacitor, “C_(REF)” represents capacitanceof said reference capacitor, “I_(SEN)” represents a magnitude of thesensing current, “V_(OFF)” represents a magnitude of the offset voltage,and “V_(REF)” represents a magnitude of the reference voltage; whereinthe central value of the sensible impedance range of saidimpedance-to-digital converter is${\frac{C_{SUB}}{C_{SEN}} \times \frac{V_{OFF}}{I_{SEN}}},$ and thesensing resolution of the impedance value sensed by saidimpedance-to-digital converter is proportional to$\frac{I_{SEN}}{V_{REF}}.$
 12. The impedance-to-digital converter ofclaim 3, wherein said offset impedance unit includes: an offsetcapacitor having a first terminal and a second terminal; an offsetresistor coupled to said offset capacitor in parallel; a first offsetswitch disposed to receive the first control signal, to introduce theoffset signal to said first terminal of said offset capacitor whenconducting, and configured to conduct or not conduct according to thefirst control signal; a second offset switch disposed to receive thefirst control signal, to couple said second terminal of said offsetcapacitor to ground when conducting, and configured to conduct or notconduct according to the first control signal; a third offset switchdisposed to receive the second control signal, having a first terminalat which the second electric charge is outputted when said third offsetswitch is conducting, a second terminal coupled to said first terminalof said offset capacitor, and configured to establish or not establishconnection between said first and second terminals thereof to beconducting or non-conducting according to the second control signal; anda fourth offset switch disposed to receive the second control signal, tointroduce the reference signal to said second terminal of said offsetcapacitor when conducting, and configured to conduct or not conductaccording to the second control signal.
 13. The impedance-to-digitalconverter of claim 12, the offset signal including an offset current,the reference signal including a reference voltage, and the to-be-sensedcomponent including a to-be-sensed resistor that has the first andsecond terminals of the to-be-sensed component, wherein said referenceimpedance unit includes a reference capacitor, and saidimpedance-to-digital converter is configured to satisfy:${{{\frac{C_{SUB}}{C_{SEN}} \times \frac{I_{OFF}}{I_{SEN}} \times R_{OFF}} - {\Delta\; R_{SEN}}} \leq R_{SEN} \leq {{\frac{C_{SUB}}{C_{SEN}} \times \frac{I_{OFF}}{I_{SEN}} \times R_{OFF}} + {\Delta\; R_{SEN}}}};{and}$$\mspace{79mu}{{{\Delta\; R_{SEN}} = {\frac{C_{REF}}{C_{SEN}} \times \frac{V_{REF}}{I_{SEN}}}};}$where “R_(SEN)” represents the impedance value of the to-be-sensedresistor sensed by said impedance-to-digital converter, “R_(OFF)”represents resistance of said offset resistor, “C_(SEN)” representscapacitance of said sensing capacitor, “C_(SUB)” represents capacitanceof said offset capacitor, “C_(REF)” represents capacitance of saidreference capacitor, “I_(SEN)” represents a magnitude of the sensingcurrent, “I_(OFF)” represents a magnitude of the offset current, and“V_(REF)” represents a magnitude of the reference voltage.
 14. Theimpedance-to-digital converter of claim 1, the to-be-sensed componenthaving a first terminal and a second terminal, wherein said sensing unitincludes: a multiplexer having a first multiplexer input to receive thesensing voltage, a second multiplexer input to receive the sensingcurrent, and a multiplexer output; a first sensing switch disposed toreceive a first control signal, having a first terminal coupled to saidmultiplexer output, and a second terminal, and configured to conduct ornot conduct according to the first control signal; a second sensingswitch disposed to receive the first control signal, having a groundedfirst terminal and a second terminal, and configured to conduct or notconduct according to the first control signal; a third sensing switchdisposed to receive a second control signal, having a first terminaldisposed to receive the reference signal, and a second terminal coupledto said second terminal of said first sensing switch, and configured toconduct or not conduct according to the second control signal; a fourthsensing switch disposed to receive the second control signal, having afirst terminal at which the first electric charge is outputted when saidfourth sensing switch is conducting, and a second terminal coupled tosaid second terminal of said second sensing switch, and configured toconduct or not conduct according to the second control signal; a sensingcapacitor having a first terminal and a second terminal; and a switchunit coupled to said second multiplexer input, said second terminal ofsaid first sensing switch, said first and second terminals of saidsensing capacitor, and said second terminal of said second sensingswitch, to be coupled to the first and second terminals of theto-be-sensed component, and operable to individually make or breakelectrical connections between said second multiplexer input and thefirst terminal of the to-be-sensed component, between said secondterminal of said first sensing switch and the first terminal of theto-be-sensed component, between the second terminal of the to-be-sensedcomponent and said second terminal of said second sensing switch,between said second terminal of said first sensing switch and said firstterminal of said sensing capacitor, and between said second terminals ofsaid sensing capacitor and said second sensing switch; wherein saidfirst sensing switch and said third sensing switch do not conduct at thesame time.
 15. The impedance-to-digital converter of claim 14, whereinsaid switch unit includes: a first switch to couple said secondmultiplexer input to the first terminal of the to-be-sensed componentwhen conducting; a second switch to couple the second terminal of theto-be-sensed component to ground when conducting; a third switch tocouple said second terminal of said first sensing switch to the firstterminal of the to-be-sensed component when conducting; a fourth switchto couple said second terminal of said second sensing switch to thesecond terminal of the to-be-sensed component when conducting; a fifthswitch coupled between said second terminal of said first sensing switchand said first terminal of said sensing capacitor; and a sixth switchcoupled between said second terminals of said sensing capacitor and saidsecond sensing switch.
 16. An impedance-to-digital converting device forsensing an impedance value of a to-be-sensed component, comprising: animpedance-to-digital converter including: a sensing unit to be coupledto the to-be-sensed component, disposed to receive a sensing voltage anda sensing current, operable to select one of the sensing voltage and thesensing current to be a sensing signal, and configured to provide thesensing signal to the to-be-sensed component, and to convert the sensingsignal into a first electric charge every operation period of saidimpedance-to-digital converter, an amount of the first electric chargebeing proportional to a magnitude of the sensing signal; an offsetimpedance unit disposed to receive an offset signal, and configured toconvert the offset signal into a second electric charge every operationperiod of said impedance-to-digital converter, an amount of the secondelectric charge being proportional to a magnitude of the offset signal;a reference impedance unit disposed to receive a reference signal and adigital signal that has a series of logic values, and including areference impedance circuit configured to convert the reference signalinto a third electric charge every operation period of saidimpedance-to-digital converter, an amount of the third electric chargebeing proportional to a magnitude of the reference signal, a polarity ofthe third electric charge being associated with a logic level of thedigital signal; and a conversion block receiving the first electriccharge, the second electric charge and the third electric charge thatare respectively outputted by said sensing unit, said offset impedanceunit and said reference impedance unit to cooperatively form a resultantelectric charge, and configured to convert the resultant electric intothe digital signal; and an operation unit coupled to said conversionblock for receiving therefrom the digital signal, and configured toperform an average operation of the series of logic values of thedigital signal to generate a series-average value; wherein saidoperation unit includes a lookup table recording a pre-stored impedancevalue that corresponds to the series-average value thus generated, andis further configured to obtain the pre-stored impedance value from saidlookup table according to the series-average value, and to output thepre-stored impedance value to serve as a sensed impedance valuecorresponding to the to-be-sensed component; wherein the impedance valuesensed by said impedance-to-digital converting device has a linearrelationship with a number of the operation periods that correspond to apredetermined logic level of the digital signal among a predeterminednumber of the operation periods; wherein a central value of a sensibleimpedance range of said impedance-to-digital converter is proportionalto a ratio of a magnitude of the offset signal to a magnitude of thesensing signal; wherein the impedance value sensed byimpedance-to-digital converting device has a sensing resolutionproportional to a ratio of the magnitude of the sensing signal to amagnitude of the reference signal.
 17. The impedance-to-digitalconverting device of claim 16, the to-be-sensed component having a firstterminal and a second terminal, wherein said sensing unit includes: amultiplexer having a first multiplexer input to receive the sensingvoltage, a second multiplexer input to receive the sensing current, anda multiplexer output; a first sensing switch disposed to receive a firstcontrol signal, having a first terminal coupled to said multiplexeroutput, and a second terminal, and configured to conduct or not conductaccording to the first control signal; a second sensing switch disposedto receive the first control signal, having a grounded first terminaland a second terminal, and configured to conduct or not conductaccording to the first control signal; a third sensing switch disposedto receive a second control signal, having a first terminal disposed toreceive the reference signal, and a second terminal coupled to saidsecond terminal of said first sensing switch, and configured to conductor not conduct according to the second control signal; a fourth sensingswitch disposed to receive the second control signal, having a firstterminal at which the first electric charge is outputted when saidfourth sensing switch is conducting, and a second terminal coupled tosaid second terminal of said second sensing switch, and configured toconduct or not conduct according to the second control signal; a sensingcapacitor having a first terminal and a second terminal; and a switchunit coupled to said second multiplexer input, said second terminal ofsaid first sensing switch, said first and second terminals of saidsensing capacitor, and said second terminal of said second sensingswitch, to be coupled to the first and second terminals of theto-be-sensed component, and operable to individually make or breakelectrical connections between said second multiplexer input and thefirst terminal of the to-be-sensed component, between said secondterminal of said first sensing switch and the first terminal of theto-be-sensed component, between the second terminal of the to-be-sensedcomponent and said second terminal of said second sensing switch,between said second terminal of said first sensing switch and said firstterminal of said sensing capacitor, and between said second terminals ofsaid sensing capacitor and said second sensing switch; wherein saidfirst sensing switch and said third sensing switch do not conduct at thesame time.
 18. The impedance-to-digital converting device of claim 17,wherein said switch unit includes: a first switch to couple said secondmultiplexer input to the first terminal of the to-be-sensed componentwhen conducting; a second switch to couple the second terminal of theto-be-sensed component to ground when conducting; a third switch tocouple said second terminal of said first sensing switch to the firstterminal of the to-be-sensed component when conducting; a fourth switchto couple said second terminal of said second sensing switch to thesecond terminal of the to-be-sensed component when conducting; a fifthswitch coupled between said second terminal of said first sensing switchand said first terminal of said sensing capacitor; and a sixth switchcoupled between said second terminals of said sensing capacitor and saidsecond sensing switch.